DOI Page / Citation link:
https://doi.org/10.11588/diglit.19574#0128
ii4 COL
Hence it is gathered, that the Colour of a body depends upon
the denfity and thickiufs of the parts of the body, between the
pores of the furface ; that the Colour is more vivid and homoge-
neous, as the parts are thinner ; that, caeteris paribus, the faid
parts are the thicken1 when the body is red, and the thinneft when
violet; that the parts of bodies are ufually much denfer than the
medium contained in their interftices ; but that, in the tails of
peacocks, fome filks, and, generally, in all bodies whofe Colour
varies according to the fituation of the eye, it is lefs; and that
the Colour of a body is the lefs vivid to the eye, as it has a denfer
medium within its pores.
Now, of the feveral opaque bodies, thofe confifting of the thin-
neft: lamellje are black ; thofe confifting either of the thickeft la-
mellae, or of lamellae very different from each other in thicknefs,
and on that account fitted to reflect all Colours, as the froth of
water, &c. are white.
Thofe again, confifting of lamellae, molt of which are of fome
intermediate thicknefs, are blue, green, yellow, or red, inafmuch
as they reflect the rays of that particular Colour much more co-
pioufly than that of any o:her Colour ; mofl of which laft they
either abforb or extinguilh, by intercepting them, or elfe they
tranfmk liiiht.
Hence it is, that fome liquors, for inftance, an infufion of lig-
num nephriticum, appear red or yellow, if viewed by reflected
light, and blue by tranfmitted light ; and leaves of gold yellow,
if viewed by reflected light, but green or blue in the latter.
To this we may add, that fome of thofe powders, ufed by
painters, have their Colour changed by being very finely ground ;
which mud be caufed by the comminution, or breaking of their
fmall parts into others {fill fmaller, juft as a lamella has its Co-
lour altered by altering its thicknefs.
In fhort, thofe odd phccnfcmena, arifing from the mixture of
liquors or different Colours, can no way be better accounted for,
than from the various actions of the faline, &c. corpufcles of one
liquor, with the coloured corpufcles of another; if they unite,
the mafs will either fvvell or (brink, and thereby its denfity will
be altered ; if they ferment, the fize of the particles may be di-
minished, and thereby the coloured liquor may become tranfpa-
rent; if they coagulate, an opaque liquor may be produced of
two tranfparent ones.
Hence it is eafy to conceive, why a coloured liquor, in a glafs
of a conical figure, placed between the eye and the light, appears
of a different Colour in different parts of the velfel; there being
more and more rays intercepted, as they pafs through a longer
or fhorter fection of the veffel, till at the bafe they are all inter-
cepted, and none feen but thofe that are reflected.
2 From
Hence it is gathered, that the Colour of a body depends upon
the denfity and thickiufs of the parts of the body, between the
pores of the furface ; that the Colour is more vivid and homoge-
neous, as the parts are thinner ; that, caeteris paribus, the faid
parts are the thicken1 when the body is red, and the thinneft when
violet; that the parts of bodies are ufually much denfer than the
medium contained in their interftices ; but that, in the tails of
peacocks, fome filks, and, generally, in all bodies whofe Colour
varies according to the fituation of the eye, it is lefs; and that
the Colour of a body is the lefs vivid to the eye, as it has a denfer
medium within its pores.
Now, of the feveral opaque bodies, thofe confifting of the thin-
neft: lamellje are black ; thofe confifting either of the thickeft la-
mellae, or of lamellae very different from each other in thicknefs,
and on that account fitted to reflect all Colours, as the froth of
water, &c. are white.
Thofe again, confifting of lamellae, molt of which are of fome
intermediate thicknefs, are blue, green, yellow, or red, inafmuch
as they reflect the rays of that particular Colour much more co-
pioufly than that of any o:her Colour ; mofl of which laft they
either abforb or extinguilh, by intercepting them, or elfe they
tranfmk liiiht.
Hence it is, that fome liquors, for inftance, an infufion of lig-
num nephriticum, appear red or yellow, if viewed by reflected
light, and blue by tranfmitted light ; and leaves of gold yellow,
if viewed by reflected light, but green or blue in the latter.
To this we may add, that fome of thofe powders, ufed by
painters, have their Colour changed by being very finely ground ;
which mud be caufed by the comminution, or breaking of their
fmall parts into others {fill fmaller, juft as a lamella has its Co-
lour altered by altering its thicknefs.
In fhort, thofe odd phccnfcmena, arifing from the mixture of
liquors or different Colours, can no way be better accounted for,
than from the various actions of the faline, &c. corpufcles of one
liquor, with the coloured corpufcles of another; if they unite,
the mafs will either fvvell or (brink, and thereby its denfity will
be altered ; if they ferment, the fize of the particles may be di-
minished, and thereby the coloured liquor may become tranfpa-
rent; if they coagulate, an opaque liquor may be produced of
two tranfparent ones.
Hence it is eafy to conceive, why a coloured liquor, in a glafs
of a conical figure, placed between the eye and the light, appears
of a different Colour in different parts of the velfel; there being
more and more rays intercepted, as they pafs through a longer
or fhorter fection of the veffel, till at the bafe they are all inter-
cepted, and none feen but thofe that are reflected.
2 From